After having the motor rebuilt a while back I have had a high oil temp problem that I haven't been able to solve. Larger cooler, larger lines with no sharp turns, syn-blend oil etc! No Better!!
Had initially ruled out the bypass valve after questioning the machine shop that did the short block. Oh no , we didn't change that..
After reading more and more about this on OSO lately I said the heck with it and ordered a 30psi bypass valve.
Decided to try to change it without pulling the motor, success!!
I was able to change the valve in my motor with very little problem.
Discovered that the machine shop had in fact replaced the original 30psi bypass valve with an 11psi one! There is a very obvious difference just by opening it in your hand with a screw driver.
Fortunately I haven't put a lot of hours on the motor and have changed oil often because i knew something wasn't right!!
There also appears to a by-pass valve up in the block in the return side, was that one ther from the factory or did the machine shop install that one as well?? This was a marine motor from the start. Should I leave it or just take it out and leave it open?? My understanding is that the one in the middle (return) is to divert oil to the oil cooler when the tapped holes in the block are utilized. Looking for an opinion from someone that has dealt with this issue successfully!

You're correct Tom. Remove that middle valve. You should not have that in a marine engine. It just restricts oil flow.

Tom,
I'm having a similar problem. Let us know if replacing the bypass with the 30 lb. one helps.

Bill

How do you remove the bypass valve? Does it destroy it? Will the machine shop or NAPA have a 30# avail or is this marine stuff? I'm building a gen6 and just about to put it together,seems the spring is really weak in the bypass,,must be the 11# one you are talking about.

Is the valve in the remote adaptor??

The valve is in the block.The 30 psi unit is available from G.M.

What happens if you plug it off to make all the oil filtered???

Like in the 350 and the 454 gen 4 oil filter adapters I drilled out and plugged to have no bypass.

The valve pops out with a little persuasion from a screw driver!
You will more than likely destroy it doing so!!
You can get the 30lb bypass valve from Jim Pace Parts. Call them and explain what you need, they have them in stock!

You can get them ( 30lb. Bypass Valves) or order them from any Chevy dealer. They are used in the 6.5L Diesel engines. They only cost about 5 bucks.

Thanks, I have removed the one in the center where the filter screws on and will replace the one flush with the block to the side with a 30#.Does this mean oil won't bypass the filter unless the restriction is 30# or ???